Question on Cell Balancing

Battery & Chargers
1

There seem to be 2 schools of thought on the need to balance Lipo Cells in a battery pack suitable for LSV/NEV , Golf Cart vehicles.

The Engineers that maintain perfect balance is required, on one hand, and the Simple KISS type individuals, among us, that want low cost and as few components as possible in our installations?

My questions.

What if you DON’T?

Is ultimate pack failure a certainty?

Will an individual cell get progressively more unbalanced or will it plateau?

Is pack efficiency the main real life problem? If so how how bad can it get?

Is a periodic equalizing charge a viable solution? If so after how many charge cycles?

Could this not be programmed into the charger?

Rodney

2

For a hobby user all that’s needed is a way to monitor cell balance.
I believe Grant may have had an issue this weekend. Waiting to hear.

There is no way to predict how long battery will stay balanced.
Imo not thru life of pack.

I think I’ve tried all the wrong ways.

Get hands-on with a pack from Mike.

Overcharged Li-Ion can be catastrophic. Best case is degraded battery.

I was a hard cell on BMS. Now I believe there is a little blue box that plugs into lithium pack, shows 24s SOC at a glance. Balances 24-7 at high rate.
Optional connections to relays limits charge/discharge.
Led/buzzer connections to warn of problems.

$300 for 24-7 protection of $1000-$3000 battery is well worth it.

When you’re ready, I’ll send you one.
Grant is testing now.

3

When I get my move done I want to get serious about a 150 AH pack for my E4 bus.

I don’t even want one extraneous component. I’m talking minimalist. I am willing to give up efficiency to gain “hands off” maintenance. I want the pack to have a projected life longer than me. (5 years minimum.)

Rodney

4

Lithium needs protection or religious monitoring. No way around it.
It can be built into the pack.
You can buy drop-in 12v lead replacements if cost is no issue.
12 Volt Lithium Ion Batteries | Drop In Replacement Batteries | Smart Battery
Almost went that way myself. As a distributor -30%

My brother was using my packs in his forklifts. Left the key on, one time, and ruined 3 cells of 24. Rest are probably damaged.

Worked most of the weekend repairing pack. Not done balancing and testing yet. Lucky they were LTO and not prone to catastrophe.

5

150 AH would be perfect. Price is the stopper.

6

I’m a dummy. Give me an overview of Volt or Leaf control system for BMS

7

This is what Grant and Mike use.

10 modules for 74v 60ah
20 for 120 ah
Should be as good as 180ah lead as you can use most of the power.

I suggest this little blue box to monitor each cell voltage.

8

Minimum connections.
Self powered from pack.
1 - 24 cells auto count and connect.
No programming.

9

Add accessories as wanted. Works fine without them.

Comes with 300a shunt
2 X temp sensors (use for motor and control if you want)
led alarm
buzzer alarm
coil drivers to relays (turn off charger or shut down car)

All prewired to plug in

Relays not included!

10

Here is one on bench.
Connected to 12s LTO (2.3v nominal)
Pre-wired leads come with it. Connect one wire to each cell+ and one to B-.

Display shows all 12 cells. Highlights high and low cells.
Values change as high cells are shunted to equalize.

11

Will it still work after 5 years outside?

12

May not be working tomorrow morning. :smiley:

Needs protection from moisture.
Could be sealed a little better.
Far as I know it’s the only game in town.